Hypothesis: Cigarette 'tar' is the major promoter of physiologic changes which are hallmarks of smoking-associated diseases. Rationale: Tobacco-heating cigarettes do not bum the tobacco contained within the cigarette and as a result reduce 'tar' inhalation by > 90%. Smokers who change to tobacco-heating cigarettes may begin to show favorable changes in the biomarkers of human disease. Methodology: Twenty-five smokers undergo a broad series of tests including heart and lung physiology, cholesterol, peripheral leukocytes and bronchoalveolar lavage. After completion of baseline studies while subjects are still smoking tobacco-burning cigarettes, subjects begin smoking tobacco-heating cigarettes. Repeat sets of tests are performed after subjects have smoked tobacco-heating cigarettes for 1 month, 6 months and 12 months. Ten non-smoking control subjects will undergo a single set of tests. Unpaired statistical comparisons are used to establish the differences in non-aasmokers and smokers while paired comparisons are used to compare serial changes in smokers from their baseline values.